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Issue 22, 2015
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Transverse migration of polyelectrolytes in microfluidic channels induced by combined shear and electric fields

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Abstract

If a dilute solution of a polyelectrolyte such as DNA is forced through a microcapillary by an electric field, while simultaneously driven by a pressure gradient, then the polymer will migrate in directions transverse to the field lines. Here we investigate the sharp increase in concentration in the center of the channel that arises when the flow and electric field drive the polymer in the same direction. We report the first systematic investigation of the effects of flow velocity, electric field, and ionic strength on the degree of migration. Our experiments show that migration increases with increasing shear and electric field as predicted by kinetic theory [Butler et al., Phys. Fluids, 2007, 19, 113101], but eventually saturates as suggested by computer simulations [Kekre et al., Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys., 2010, 82, 050803(R)]. The addition of salt reduces the strength of the migration, consistent with a screening of long-range hydrodynamic flow fields by added salt. However, increasing the ionic strength of a Tris–acetate–EDTA buffer solution has much less effect on the degree of migration.

Graphical abstract: Transverse migration of polyelectrolytes in microfluidic channels induced by combined shear and electric fields

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Publication details

The article was received on 09 Mar 2015, accepted on 16 Apr 2015 and first published on 16 Apr 2015


Article type: Paper
DOI: 10.1039/C5SM00572H
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Soft Matter, 2015,11, 4375-4382

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    Transverse migration of polyelectrolytes in microfluidic channels induced by combined shear and electric fields

    M. Arca, J. E. Butler and A. J. C. Ladd, Soft Matter, 2015, 11, 4375
    DOI: 10.1039/C5SM00572H

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